To heat or not to heat: a study of the performances of iron carbide nanoparticles in magnetic heating

Abstract

Heating magnetic nanoparticles with high frequency magnetic fields is a topic of interest for biological applications (magnetic hyperthermia) as well as for heterogeneous catalysis. This study shows why FeC NPs of similar structures and static magnetic properties display radically different heating power (SAR from 0 to 2 kW.g -1 ). By combining results from Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS) and static and time-dependent high-frequency magnetic measurements, we propose a model describing the heating mechanism in FeC nanoparticles. Using, for the first time, time-dependent highfrequency hysteresis loop measurements, it is shown that in the samples displaying the larger heating powers, the hysteresis is strongly time dependent. More precisely, the hysteresis area increases by a factor 10 on a timescale of a few tens of seconds. This effect is directly related to the ability of the nanoparticles to form chains under magnetic excitation, which depends on the presence or not of strong dipolar couplings. These differences are due to different ligand concentrations on the surface of the particles. As a result, this study allows the design of a scalable synthesis of nanomaterials displaying a controllable and reproducible SAR.

Engineering Iron–Nickel Nanoparticles for Magnetically Induced CO2Methanation in Continuous Flow

“…When comparing structural characterization of 1 and 2 (Figure a,b), no significant differences were observed neither in the XRD patterns nor in the static magnetic properties measured by VSM at 300 K (see also the Supporting Information, Figure S10 for VSM at 5 K). However, the SAR of the NPs 2 dropped from 600 to 350 W g −1 after Ni enrichment (Figure c), as expected after the addition of a softer material such as Ni …”

“…However, the SAR of the NPs 2 dropped from 600 to 350 W g À1 after Ni enrichment (Figure 1 c), as expected after the addition of a softer material such as Ni. [39] NPs 2 were supported on SiRAlOx (Supporting Information, Figure S11) and evaluated for CO 2 hydrogenation. As expected, 2/SiRAlOx displayed a slightly higher amount of Ni by ICP-MS than NPs 1/SiRAlOx (6.1 wt % vs. 5.6 wt % respectively), but a comparable Fe content (2.0 wt % vs. 1.8 wt %).…”

Tuning the Composition of FeCo Nanoparticle Heating Agents for Magnetically Induced Catalysis

“…It has been reported that the heating threshold for FeC-NPs corresponds to an amplitude of 30 mT and that these NPs display a remarkably high heating capability at 48 mT (up to 2000 W/g). 25 On the other hand, Fe-NPs start heating at higher amplitudes (>35mT) and reach 820 W/g at 48 mT, while alloying Fe with At the opposite, low anisotropy NPs such as the Fe 0.5 Co 0.5 display a SAR starting to increase at low field and their SAR(µ 0 H) has a higher slope. If these MNPs were measured at very high field, the high-anisotropy NPs would have a much larger SAR than the low-anisotropy ones.…”

Internal Temperature Measurements by X-Ray Diffraction on Magnetic Nanoparticles Heated by a High-Frequency Magnetic Field

“…In this case, experiments would conclude to a local heating even though there is none. With respect to ii), it is a well-known fact that, in liquid phase, MNPs excited by an external magnetic field form chains, which are sometimes several tens or hundreds of microns wide, depending on the MNP properties, their functionalization, the magnetic field amplitude, and so forth 39,40,41,42 . When such chains form, the measured "local" temperature is not the temperature at the surface of an isolated nanoscale object, but the temperature at the surface and/or inside a micron-scale magnetically heated assembly of MNPs.…”